otn tour 2016 - dba commands and concepts that every developer should know

DBA Commands and Concepts That Every Developer Should

Know

Presented by: Alex Zaballa, Oracle DBA

Alex Zaballa

http://alexzaballa.blogspot.com/

@alexzaballa206 and counting…https://www.linkedin.com/in/alexzaballa

Worked for 7 years in Brazil as an Oracle Developer.2000 - 2007

Worked for 8 years in Angola as an Oracle DBAfor the Ministry of Finance.2007 - 2015

Availability of Oracle Database 12.2

Oracle Announces Beta Availability of Oracle Database 12c Release 2 - Oct 26, 2015

• PLUGGABLE DATABASES From 252 to 4096

• HOT CLONING Don’t need to put the source in read-only for cloning

• SHARDING It’s like partitioning in a shared nothing database

The data is split into multiple databases

• In-Memory In-Memory column Store on Active Data Guard

Heat Map

• APPLICATION CONTAINER Pluggable Databases will share application objects

• More isolation, resource manager will limit the memory in addition to CPU and I/O.• AWR will work on Active Data Guard Database: you can tune your reporting database

Availability of Oracle Database 12.2

Source: https://blogs.oracle.com/UPGRADE/entry/oracle_database_12_2_just

Oracle Database Release StatusMOS Note:742060.1

DBA Commands and Concepts That Every Developer Should Know

No DBA access to the Database?


eDB360 sample


SQLD360 sample

insert /*+ append parallel */ into tab1 select /*+ parallel */ * from tab2 nologging;15 minutes to complete.

create table tab1 as select /*+ parallel */ * from tab2 nologging;2 minutes to complete.

Parallel

Parallel

Source: https://docs.oracle.com/database/121/VLDBG/GUID-5EB01FA8-030B-45BB-9B16-2D13881F6010.htm

Parallel

Parallel

Update I$_2258193201set IND_UPDATE = 1where exists (

select 1from XX Twhere I$_2258193201.X_REF_DT = T.X_REF_DTand I$_2258193201XX.X_ACCT_KEY =

T.X_ACCT_KEY);

60 minutes to complete.

Parallel

Update /*+ PARALLEL */ I$_2258193201_NEW I$_2258193201set IND_UPDATE = 1where exists (

select /*+ PARALLEL */ 1from XX_NEW Twhere I$_2258193201.X_REF_DT = T.X_REF_DTand I$_2258193201XX.X_ACCT_KEY =

T.X_ACCT_KEY);


***Duplicate tables “_NEW”

Parallel

Update /*+ PARALLEL */ I$_2258193201set IND_UPDATE = 1where exists (

select /*+ PARALLEL */ 1from XX Twhere I$_2258193201.X_REF_DT = T.X_REF_DTand I$_2258193201XX.X_ACCT_KEY =

T.X_ACCT_KEY);


Parallel

Full Table Scan: db file scattered read

Parallel

Row chaining/Migration

"A migrated row is a row that was moved to another block due to an update making it too large to fit on its original block with the other rows there”

"Any table with a long/long raw will have chained rows”

"Any table with more than 255 columns will have chained rows”

"Any table whose rowsize exceeds the blocksize will have chained rows"

Increasing PCTFREE can help to avoid migrated rows.

Explain Plan

How many people are using Explain Plan ?

Explain Plan

Explain Plan Lies

Explain Plan

Explain Plan just try to predict the Plan.

AUTOTRACE experiences a similar "problem”, especially when the SQL statement uses bind variables.

Explain Plan

Solution ?

DBMS_XPLAN.DISPLAY_CURSOR

Oracle Flashback Query

• Flashback Query (SELECT AS OF) AS OF TIMESTAMP

• Flashback Version Query VERSIONS BETWEEN { SCN | TIMESTAMP } start

AND end

• Flashback Transaction Query SELECT FROM flashback_transaction_query

• Retrieve old versions of procedures:

select text from dba_source as of timestamp systimestamp - interval '5' minute where name='MY_PROC' order by line;



The maximum available versions are dependent on the UNDO_RETENTION parameter.

The default is 900 seconds (15 minutes).

Oracle Flashback Table

Reinstating an accidentally dropped table.

Parameter recyclebin = on (default).

SELECT OWNER,OBJECT_NAME, ORIGINAL_NAME, TYPE, DROPTIMEFROM DBA_RECYCLEBIN WHERE ORIGINAL_NAME='TAB_TEST';

FLASHBACK TABLE TAB_TEST TO BEFORE DROP;

Oracle Flashback Table

RMAN Table Recovery in 12c

RMAN enables you to recover one or more tables or table partitions to a specified point in time.

RMAN Table Recovery in 12c

RMAN> RECOVER TABLE HR.REGIONS UNTIL TIME "TO_DATE('01/10/2013 09:33:39','DD/MM/RRRR HH24:MI:SS')"AUXILIARY DESTINATION '/tmp/backups'

Schema Management DDL Wait Option

SQL> alter table invoice add (code number);

alter table invoice add (code number) *ERROR at line 1:ORA-00054: resource busy and acquire with NOWAIT specified or timeout expired

Schema Management DDL Wait Option

Parameter DDL_LOCK_TIMEOUT (default = 0)

It will wait for N seconds. In that N seconds, it continually re-tries the DDL operation until it's successful or this time expires.

Schema ManagementAdding Columns with a Default Value

Table T1 3 millions rows

10.2.0.4.0 > alter table t1 add C_DDL number default 42 not null;Table altered.Elapsed: 00:00:48.53

11.2.0.3.0> alter table t1 add C_DDL number default 42 not null;Table altered.Elapsed: 00:00:00.04

http://www.oracle.com/technetwork/pt/articles/sql/otimizacao-comandos-ddl-oracle-11g-2226731-ptb.html

Rollback

How much longer?

select * from v$session_longopswhere sid = sid_of_the_session_doing_rollback

Rollback

Source: https://docs.oracle.com/cloud/latest/db121/REFRN/refrn30227.htm#REFRN30227

RollbackSID : 26SERIAL# : 30832OPNAME : Transaction RollbackTARGET :TARGET_DESC : xid:0x000e.01c.00000012SOFAR : 1211TOTALWORK : 21244UNITS : BlocksSTART_TIME : 15-nov-2015 16:20:07LAST_UPDATE_TIME : 15-nov-2015 16:21:24TIME_REMAINING : 55ELAPSED_SECONDS : 5CONTEXT : 0MESSAGE : Transaction Rollback: .... USERNAME : alex_zaballaSQL_ADDRESS : 00000000DF79A840SQL_HASH_VALUE : 72257521SQL_ID : 4wv9a0h24x3zj

Pending Statistics

We have the option of keeping the newly gathered statistics in a pending state for testing purposes, until you choose to publish them.

Set table preferences: begin dbms_stats.set_table_prefs ( ownname => 'SCOTT', tabname => 'EMP', pname => 'PUBLISH', pvalue => 'FALSE' ); end;

Collect the statistics.

Pending Statistics

select num_rows, to_char(last_analyzed,'dd/mm/rrrr hh24:mi:ss')from all_tab_pending_statswhere table_name = 'EMP';

Pending Statistics

alter session set optimizer_use_pending_statistics = true;

Test the queries.

Pending Statistics

If it’s ok:

dbms_stats.publish_pending_stats('SCOTT', 'EMP');

Or:

dbms_stats.delete_pending_stats(’SCOTT',’EMP');

Restore Statistics from History

Check the retention:

select DBMS_STATS.GET_STATS_HISTORY_RETENTION from dual;

Default is 31 days.


Statistics available for the table:

SELECT OWNER, TABLE_NAME, STATS_UPDATE_TIME FROM dba_tab_stats_historyWHERE table_name='MY_TABLE';


Begin dbms_stats.restore_table_stats( 'SCOTT', 'EMP', ‘08-NOV-15 11.38.05.015640 AM +08:00’);End;

Export and Import schema statisticsbegin dbms_stats.CREATE_STAT_TABLE( ownname=>user , stattab=>'MY_STATS_TABLE' );end;

begin dbms_stats.export_schema_stats( ownname=>user , stattab=>'MY_STATS_TABLE' , statid=>'CURRENT_STATS' );End;

EXPDP / IMPDP

begin dbms_stats.import_schema_stats( ownname=>user , stattab=>'MY_STATS_TABLE' , statid=>'CURRENT_STATS' );End;

DBMS_APPLICATION_INFO

Allows programs to add information to the V$SESSION.

Use SET_MODULE to set the name for the program that the user is currently executing. Optionally you can also set an action name.

Use SET_ACTION for subsequent processing.

Use SET_CLIENT_INFO for any additional information.

Row-by-Row Processing vs Bulk Processing

Instead of fetching a single row at a time it is possible to use the bulk features.

Oracle Virtual Private Database (VPD)

• VPD enables you to create security policies to control database access at the row and column level.

• VPD adds a dynamic WHERE clause to a SQL statement.

• VPD enforces security directly on database tables, views, or synonyms.

Oracle Virtual Private Database (VPD)

Original Select:

SELECT * FROM ORDERS;

VPD policy dynamically appends:

SELECT * FROM ORDERS WHERE COMPANY_ID = 1;

otn tour 2016 - dba commands and concepts that every developer should know

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